U.S. patent number 6,780,271 [Application Number 09/582,069] was granted by the patent office on 2004-08-24 for method for continuous, solvent and mastication-free production of pressure-sensitive self-adhesive materials based on non-thermoplastic elastomers and their coating for the production of self-adhesive articles.
This patent grant is currently assigned to tesa AG. Invention is credited to Axel Burmeister, Sven Hansen, Frank Henke, Ralf Hirsch, Heiko Leydecker, Klaus Massow, Jochen Stahr.
United States Patent |
6,780,271 |
Burmeister , et al. |
August 24, 2004 |
METHOD FOR CONTINUOUS, SOLVENT AND MASTICATION-FREE PRODUCTION OF
PRESSURE-SENSITIVE SELF-ADHESIVE MATERIALS BASED ON
NON-THERMOPLASTIC ELASTOMERS AND THEIR COATING FOR THE PRODUCTION
OF SELF-ADHESIVE ARTICLES
Abstract
Process for the continuous solvent-free and mastication-free
production of self-adhesive compositions based on non-thermoplastic
elastomers in a continuously operating apparatus having a filling
section and a compounding section, comprising a) feeding the solid
components of the self-adhesive composition, such as elastomers and
resins, into the filling section of the apparatus, optionally
feeding of fillers, colorants and/or crosslinkers, b) transferring
the solid components of the self-adhesive composition from the
filling section to the compounding section, c) adding the liquid
components of the self-adhesive composition, such as plasticizers,
crosslinkers and/or further tackifier resins to the compounding
section, d) preparing a homogeneous self-adhesive composition in
the compounding section, and e) discharging the self-adhesive
composition.
Inventors: |
Burmeister; Axel (Hamburg,
DE), Hansen; Sven (Hannover, DE), Henke;
Frank (Neu Wulmstorf, DE), Hirsch; Ralf
(Quickborn, DE), Leydecker; Heiko (Norderstedt,
DE), Massow; Klaus (Hamburg, DE), Stahr;
Jochen (Hannover, DE) |
Assignee: |
tesa AG (Hamburg,
DE)
|
Family
ID: |
7858056 |
Appl.
No.: |
09/582,069 |
Filed: |
June 21, 2000 |
PCT
Filed: |
February 13, 1999 |
PCT No.: |
PCT/EP99/00968 |
PCT
Pub. No.: |
WO99/42276 |
PCT
Pub. Date: |
August 26, 1999 |
Foreign Application Priority Data
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|
|
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Feb 18, 1998 [DE] |
|
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198 06 609 |
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Current U.S.
Class: |
156/244.11;
156/244.27; 264/211.23; 264/211; 156/338; 264/176.1 |
Current CPC
Class: |
C09J
7/381 (20180101); B29B 7/487 (20130101); B29C
48/154 (20190201); B29B 7/86 (20130101); B29C
43/24 (20130101); B29C 48/435 (20190201); B29C
48/425 (20190201); B29B 7/7495 (20130101); B05D
5/10 (20130101); B29B 7/485 (20130101); B29B
7/845 (20130101); B29B 7/488 (20130101); B29C
48/44 (20190201); B29C 48/305 (20190201); B29C
48/08 (20190201); B29B 7/72 (20130101); B29B
7/823 (20130101); B05D 1/28 (20130101); C09J
2453/00 (20130101); B29K 2019/00 (20130101); B05D
1/265 (20130101); B29B 7/90 (20130101); B29K
2009/06 (20130101) |
Current International
Class: |
B29C
47/42 (20060101); B29C 47/14 (20060101); B29C
47/38 (20060101); B05D 5/10 (20060101); C09J
7/02 (20060101); B29C 43/24 (20060101); B29C
47/02 (20060101); B05D 1/28 (20060101); B05D
1/26 (20060101); B29C 047/00 () |
Field of
Search: |
;425/94,97,101
;427/208.4,294,516 ;428/492
;156/244.11,244.27,244.23,244.24,326,331.7,338
;264/176.1,211,211.12,211.21,211.23,211.24,216 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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23 03 366 |
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Jul 1974 |
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DE |
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25 21 774 |
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Nov 1976 |
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DE |
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31 33 647 |
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Mar 1983 |
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DE |
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39 08 415 |
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Sep 1990 |
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DE |
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44 33 487 |
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Mar 1996 |
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DE |
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195 18 255 |
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Nov 1996 |
|
DE |
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196 34 813 |
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Mar 1997 |
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DE |
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9421955 |
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May 1997 |
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DE |
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94 21 955 |
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Jun 1997 |
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DE |
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196 31 182 |
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Jul 1997 |
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DE |
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0 818 521 |
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Jan 1998 |
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EP |
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0 874 034 |
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Oct 1998 |
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EP |
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2 274 429 |
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Jul 1994 |
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GB |
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WO 94/11175 |
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Oct 1993 |
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WO |
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WO 95/25774 |
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Feb 1995 |
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WO |
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WO 97/07963 |
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Jul 1996 |
|
WO |
|
Other References
Derwent Abstract ACC-NO 1997-260140, DE 9421955 U1.* .
Patent Abstracts of Japan vol. 098, No. 014, Dec. 31, 1998 & JP
10 259359 A (OJI Paper Co., Ltd.), Sep. 29, 1998. .
CIPO--Canadian Patent Database--Details--698518. .
Derwent Abstract JP 07324182 A. .
Derwent Abstract JP 07278509 A. .
Derwent Abstract JP 07331197 A..
|
Primary Examiner: Ball; Michael W.
Assistant Examiner: Corcoran; Gladys
Attorney, Agent or Firm: Norris McLaughlin & Marcus
Claims
What is claimed is:
1. A process for the continuous solvent-free and mastication-free
production of self-adhesive compositions comprising rubber having a
molecular weight M.sub.w.gtoreq.1 million in a continuously
operating planetary roll extruder having a filling section and a
compounding section, comprising a) feeding solid components of the
self-adhesive composition, including rubber having a molecular
weight M.sub.w.gtoreq.1 million, into the filling section of the
planetary roll extruder, optionally with fillers, colorants,
crosslinkers, or a combination thereof, b) transferring the solid
components of the self-adhesive composition from the filling
section to the compounding section, c) adding liquid components of
the self-adhesive composition to the compounding section, d)
preparing a homogeneous self-adhesive composition in the
compounding section, and e) discharging the self-adhesive
composition.
2. Process according to claim 1, wherein said compounding section
of said planetary roll extruder has at least two coupled roll
cylinders.
3. Process according to claim 2, wherein each roll cylinder of the
planetary roll extruder contains at least half the maximum number
of planetary spindles that each is capable of accommodating.
4. Process according to claim 1, wherein, following its discharge
from the apparatus the self-adhesive composition is freed from gas
bubbles under the effect of reduced pressure.
5. Process according to claim 1, wherein said discharged
self-adhesive composition is conveyed into a coating device and
further comprising the step of coating the self-adhesive
composition with the coating device onto a material in web
form.
6. Process according to claim 5, wherein said discharged
self-adhesive composition is conveyed to said coating device by a
melt pump or a conveying extruder for conveying the adhesive
composition, which is operated with rotational speed regulation or
pressure regulation, and is arranged between the planetary roll
extruder and the coating device.
7. Process according to claim 5, wherein the coating of the
web-form material takes place with a roll mill or calender unit,
the self-adhesive composition being shaped to the desired thickness
as it passes through one or more roll nips prior to transfer to the
web-form material.
8. Process according to claim 5, wherein the coating of the
web-form material takes place with an extrusion die fed by an
extruder.
9. Process according to claim 8, wherein the extrusion die is
configured as a coathanger manifold die.
10. Process according to claim 5, wherein the coated material is
crosslinked in a step subsequent to the step of coating.
11. Process according to claim 10, wherein the coated material is
crosslinked by means of electron beams without promoters.
12. Process according to claim 10, wherein the coated material is
thermally crosslinked.
13. Process according to claim 1, wherein at the exit from the
apparatus the self-adhesive composition has a temperature of less
than 150.degree. C.
14. Process according to claim 1, wherein said self-adhesive
compositions comprise components selected from the group consisting
of natural rubbers, randomly copolymerized styrene-butadiene
rubbers (SBR), butadiene rubbers (BR), synthetic polyisoprenes
(IR), butyl rubbers (IIR), halogenated butyl rubbers (XIIR),
acrylate rubbers (ACM), ethylene vinyl acetate copolymers (EVA),
polyolefins, polyurethanes and blends thereof.
15. Process according to claim 1, wherein said compositions
comprise thermoplastic and non-thermoplastic elastomers, the
thermoplastic elastomers comprising from 10 to 50% by total weight
of elastomers.
16. Process according to claim 1, wherein the crosslinkers are
selected from the group consisting of sulphur systems, accelerated
sulphur systems, reactive phenolic resin systems and diisocyanate
crosslinking systems.
17. Process according to claim 1, wherein the crosslinkers are
heat-activatable.
18. Process according to claim 2, wherein said planetary roll
extruder has three coupled roll cylinders.
19. Process according to claim 3, wherein each roll cylinder
contains more than 3/4 the maximum number of planetary spindles
that each is capable of accommodating.
20. Process of claim 6, wherein said conveying extruder is a
devolatilizing extruder which is operated with pressure
regulation.
21. Process of claim 13, wherein said temperature is between
70.degree. C. and 110.degree. C.
22. Process of claim 17, wherein said crosslinkers are
heat-activatable at temperatures of from 110-140.degree. C.
Description
The present invention relates to a process for the continuous,
solvent- and mastication-free production of pressure-sensitive
self-adhesive compositions based on non-thermoplastic elastomers,
using tackifier resins, typical rubber plasticizers, optionally
fillers and heat-activatable crosslinkers, and to the coating
thereof to produce self-adhesive articles, in particular
high-performance self-adhesive tapes.
BACKGROUND OF THE INVENTION
Fundamental to the profile of performance requirements of
pressure-sensitive adhesive systems and the pressure-sensitive
adhesive articles produced with them are the two physical phenomena
of adhesion and cohesion. Adhesion is dealt with in the technical
jargon using the terms instant bond strength (tack) and bond
strength (peel strength) and describes by definition the terms
"self-adhesive" and/or "pressure-sensitive adhesive", i.e.
permanent adhesive bonding under "gentle pressure".
Especially in the case of pressure-sensitive adhesives based on
natural rubber, this property is obtained by mixing in tackifier
resins (tackifiers) and plasticizers having relatively low
molecular weights.
The second defining property of the pressure-sensitive adhesives is
their simple residue-free redetachability after use. This property
is determined essentially by the high molecular mass rubber
fractions as the elastomer component, which give the system, in the
form of cohesion (internal strength), the required strength under
shear stress, which is of particular significance for the use of
the products at relatively high temperatures and/or mechanical
loads. By additional crosslinking, for example by way of ionizing
rays, reactive resin components or other chemical crosslinkers,
this property can be reinforced.
The performance of the pressure-sensitive adhesive is, therefore,
critically determined by the balanced proportion of adhesion
properties and cohesion properties and by compatibility,
homogeneity and stability of the blend of components with extremely
high and relatively low average molecular weights, something which
is relatively easy to achieve in the case of production of the
composition in industry-standard mixers and kneading machines using
solvents.
The solvent-free compounding and processing of self-adhesive
compositions, on the other hand, has become established primarily
only for the processing of elastomers which melt, so-called
thermoplastic elastomers.
In this case, the process of producing the composition is normally
conducted in the melt in twin-screw extruders at relatively high
temperatures, with coating taking place normally by means of slot
dies.
The advantage of using thermoplastic elastomers lies essentially in
a simplification of the coating process. The avoidance of flammable
solvents does away with the need for the drier units, with their
high energy consumption for the evaporation and recovery of the
solvents, and to use explosion-protected units. Hot-melt coating
units are compact and permit much higher coating speeds. Moreover,
the technology is an environment-friendly one in which there are no
solvent emissions.
For the solvent-free compounding of thermoplastic elastomers, the
prior art makes use predominantly of block copolymers having
polystyrene block fractions. The advantage of this class of
substance is that the polystyrene domains present in the polymer
soften above 100.degree. C., accompanied by a sharp fall in the
viscosity of the adhesive composition and thereby providing ease of
processing. After cooling to room temperature, the polystyrene
domains are reformed and impart a certain shear strength to the
pressure-sensitive adhesives based on thermoplastic elastomers.
The thermoplastic elastomers can be compounded faultlessly in the
extruder process using hydrocarbon resins which promote bond
strength. In this way, a desired level of bond strength can be
achieved with relative ease. The resultant pressure-sensitive
adhesives, however, remain sensitive to temperatures above
40.degree. C. For the self-adhesive tapes produced on this basis,
this remanent "creep behaviour" is critical for unrestricted
storage stability (blocking of the rolls in the stack, especially
in the course of transportation in relatively warm climate zones)
and for their use at relatively high operating temperatures (for
example as masking tapes in automotive finishing, where despite
postcrosslinking such tapes lose their functional capacity: the
pressure-sensitive adhesive softens and the shear strength for
fixing the masking papers is no longer ensured).
For this reason, the known hot-melt pressure-sensitive adhesives
based on block copolymers have been able to establish themselves
almost exclusively for packaging tapes and for labels for use at
room temperatures.
Using non-thermoplastic elastomers, such as natural rubber, on the
other hand, it is possible to achieve the required shear strengths;
however, the solvent-free production and processing of
natural-rubber pressure-sensitive adhesives has to date confronted
the person skilled in the art with unsolved problems.
Owing to the extremely high molecular mass fractions of the rubber
(with M.sub.w.gtoreq.1 million), solvent-free self-adhesive
compositions cannot be processed by the hot-melt pressure-sensitive
adhesive technology, or else the rubbers used must be reduced in
their molecular weight (broken down) so greatly before processing
that as a result of this breakdown their suitability for
high-performance self-adhesive compositions is impaired.
The deliberate industrial process of rubber breakdown under the
combined action of shear stress, temperature and atmospheric oxygen
is referred to in the technical literature as mastication and is
generally carried out in the presence of chemical auxiliaries,
which are known from the technical literature as masticating agents
or peptizers, or, more rarely, as "chemical plasticizing aids". In
rubber technology, the mastication step is necessary in order to
make it easier to integrate the additives.
This mastication must be clearly distinguished from the breakdown
known as degradation which results in all of the standard
solvent-free polymer technologies, such as compounding, conveying
and coating in the melt. Uncontrolled degradation often constitutes
an unwanted phenomenon. It can be minimized by providing an inert
gas atmosphere.
A variety of routes to the solvent-free production and processing
of rubber pressure-sensitive adhesives have been described.
The patent CA 698 518 describes a process for achieving production
of a composition by adding high proportions of plasticizer and/or
simultaneously strong mastication of the rubber. Although this
process can be used to obtain pressure-sensitive adhesives having
an extremely high tack, user-compatible shear strength, even with a
relatively high level of subsequent crosslinking, can be achieved
only to a limited extent owing to the relatively high plasticizer
content or else to the severe breakdown in molecular structure of
the elastomer to a molecular weight average of M.sub.w.ltoreq.1
million.
The use of polymer blends, where besides non-thermoplastic natural
rubber use is also made of block copolymers, in a ratio of
approximately 1:1, is essentially an unsatisfactory compromise
solution, since it results neither in high shear strengths when the
self-adhesive tapes are used at relatively high temperatures nor in
significant improvements relative to the properties described in
the patent.
JP 07 324 182 A2 describes a multistage process in which a
double-sided adhesive tape has a pressure-sensitive adhesive layer
based on an acrylic resin adhesive and has a second layer
comprising a blend of isoprene-styrene elastomer, natural rubber
and non-reactive hydrocarbon resin (Arkon P 100). This tape is used
as a carpet-laying tape, where there are likewise no stringent
requirements on the shear strength at elevated temperatures.
The use of non-thermoplastic elastomers is also described in JP 95
331 197, where use is made of an isocyanate-reactive natural rubber
(polyisoprene grafted with maleic ester) having an average
molecular weight of below 1 million with aliphatic non-reactive
hydrocarbon resins, which is crosslinked with blocked isocyanates
(for example Desmodur CT); the mixture is initially crosslinked at
150.degree. C. for five minutes and following its subsequent
coating onto PET film is cured at 180.degree. C. for several
minutes (for example 15 minutes). This procedure clearly shows how
complicated it is to achieve postcrosslinking if the natural rubber
is subjected to excessive breakdown during the production
process.
The patent application JP 95 278 509 protects a self-adhesive tape
in which the natural rubber is masticated to an average molecular
weight of M.sub.w =100,000 to 500,000 in order to obtain a coatable
homogeneous mixture comprising hydrocarbon resins,
rosin/rosin-derivative resins and terpene resins, which can be
processed readily at between 140.degree. C. and 200.degree. C. with
a coating viscosity of from 10 to 50.times.10.sup.3 cps but require
an extremely high subsequent EBC dose (40 Mrad) in order to ensure
the shear strength necessary for their use. For carrier materials
such as impregnated and/or sized papers, and for woven carriers
based on viscose staple and the like, the system is not very
suitable, since at the necessarily high beam doses there is
significant carrier deterioration.
The use of exclusively non-thermoplastic rubbers as the elastomer
component in the formulation of pressure-sensitive adhesives with
the existing cost advantage possessed by, for example, natural
rubbers over the standard commercial block copolymers, and the
outstanding properties, especially the shear strength of natural
rubber and of corresponding synthetic rubbers, is also set out at
length in the patents WO 94 11 175, WO 95 25 774, WO 97 07 963 and,
correspondingly, U.S. Pat. Nos. 5,539,033 and 5,550,175. In these
cases, the additives customary in pressure-sensitive adhesive
technology, such as tackifier resins, plasticizers and fillers, are
described.
The production process disclosed in each case is based on a
twin-screw extruder which permits compounding to a homogeneous
pressure-sensitive adhesive blend with the chosen process regime,
involving mastication of the rubber and subsequent gradual addition
of the individual additives with an appropriate temperature
regime.
The mastication step of the rubber, which precedes the actual
production process, is described at length. It is necessary and
characteristic of the process chosen, since with the technology
chosen therein it is indispensable to the subsequent integration of
the other components and to the extrudability of the blended
composition. Also described is the feeding in of atmospheric
oxygen, as recommended by R. Brzoskowski, J. L. and B. Kalvani in
Kunststoffe 80 (8), (1990), p. 922 ff., in order to accelerate
mastication of the rubber.
This procedure makes it absolutely necessary to practise the
subsequent step of electron beam crosslinking (EBC) and to use
reactive substances as EBC promoters in order to achieve an
effective crosslinking yield.
Both process steps are described in the abovementioned patents, but
the EBC promoters chosen also tend towards unwanted chemical
crosslinking reactions at elevated temperatures, which limits the
use of certain tackifier resins.
Owing to the unavoidable high product temperatures, compounding in
a twin-screw extruder prevents the use of heat-activatable
substances suitable for crosslinking the adhesive compositions,
such as, for example, reactive (optionally halogenated) phenolic
resins, sulphur or sulphur-donor crosslinker systems, since the
chemical crosslinking reactions which ensue in the process result
in such a great increase in viscosity that the coatability of the
resulting pressure-sensitive adhesive composition is impaired.
In summary, it can be stated that all of the known processes are
characterized by extremely severe rubber breakdown. When the
compositions are processed further into self-adhesive tapes, this
necessitates extreme crosslinking conditions and results, moreover,
in a partially restricted applications profile, especially as
regards the use of resultant self-adhesive tapes at elevated
temperatures.
There is numerous known apparatus for the continuous production and
processing of solvent-free polymer systems. In common use are screw
machines such as single-screw and twin-screw extruders in a variety
of process lengths and with a variety of fittings. However,
continuously operating kneading apparatus of a very wide variety of
constructions, including, for example, combinations of kneading and
screw machines, or else planetary roll extruders, are also used for
this purpose.
Planetary roll extruders have been known for a fairly long time and
were first used in the processing of thermoplastics such as PVC,
for example, where they were used primarily to supply the
downstream units such as, for example, calenders or roll mills. As
a consequence of their advantage of the great renewal of surface
area for material exchange and heat exchange, by means of which the
frictional energy can be dissipated rapidly and effectively, and
because of the low residence time and the narrow residence-time
spectrum, their use in recent times has been extended, inter alia,
to compounding processes which require a particular
temperature-controlled regime.
Depending on manufacturer, planetary roll extruders are available
in various designs and sizes. The diameters of the roll cylinders,
depending on the desired throughput, are typically between 70 mm
and 400 mm.
Planetary roll extruders generally have a filling section and a
compounding section. The filling section consists of a conveying
screw to which all of the solid components are fed continuously.
The conveying screw then passes the material to the compounding
section. The area of the filling section, together with the screw,
is preferably cooled in order to prevent baking-on of materials on
the screw. Alternatively, there are designs without a screw
section, where the material is fed directly between central
spindles and planetary spindles. However, this is not important for
the effectiveness of the process of the invention.
The compounding section consists of a driven central spindle and a
number of planetary spindles which rotate around the central
spindle within a roll cylinder with internal helical gearing. The
rotary speed of the central spindle and hence the rotational speed
of the planetary spindles can be varied and is therefore an
importance parameter for the control of the compounding process.
The materials are circulated between the central and planetary
spindles, or between the planetary spindles and the helical gearing
of the roll section, so that under the influence of shear energy
and external heating the materials are dispersed to form a
homogeneous compound.
The number of planetary spindles rotating in each roll cylinder can
be varied and thus adapted to the requirements of the process. The
number of spindles influences the free volume within the planetary
roll extruder, and the residence time of the material in the
process, and also determines the surface area for heat and material
exchange. By way of the shear energy introduced, the number of
planetary spindles has an influence on the result of compounding.
Given a constant diameter of roll cylinder, a larger number of
spindles permits better homogenization and dispersion or,
respectively, a greater product throughput.
The maximum number of planetary spindles installable between the
central spindle and the roll cylinder depends on the diameter of
the roll cylinder and on the diameter of the planetary spindles
used. When using relatively large roll diameters, as required for
obtaining production-scale throughputs, and/or relatively small
diameters for the planetary spindles, the roll cylinders can be
equipped with a relatively large number of planetary spindles. With
a roll diameter of D=70 mm, typically up to seven planetary
spindles are used, whereas with a roll diameter of D=200 mm ten,
for example, and with a roll diameter of D=400 mm 24 for example,
planetary spindles can be used.
In this context, reference is made to the patent applications and,
respectively, utility model DE 196 31 182, DE 94 21 955, DE 195 34
813, DE 195 18 255 and DE 44 33 487, which give an overview of the
prior art in the field of planetary roll extruders.
Thus, furthermore, DE 39 08 415 A1 describes the processing of
rubber mixtures or rubberlike mixtures by means of planetary roll
extruders. For the purpose of further processing on downstream
equipment, pre-batches or finished mixtures are masticated and
plastified on a planetary roll extruder. Likewise described is the
production of finished mixtures in a planetary roll extruder: in
this case vulcanizing systems and other components are metered into
the rubber premixes.
The object of the present invention was to provide a process with
which pressure-sensitive self-adhesive compositions based on
non-thermoplastic elastomers can be produced continuously without
solvent, with or without the use of thermally reactive components,
and, if desired, can be coated in-line without the need for
property-impairing mastication of the rubber.
SUMMARY OF THE INVENTION
The invention accordingly provides a process for the continuous
solvent-free and mastication-free production of self-adhesive
compositions based on non-thermoplastic elastomers in a
continuously operating apparatus having a filling section and a
compounding section, comprising the following steps: a) feeding the
solid components of the self-adhesive composition, such as
elastomers and resins, into the filling section of the apparatus,
optionally feeding of fillers, colorants and/or crosslinkers, b)
transferring the solid components of the self-adhesive composition
from the filling section to the compounding section, c) adding the
liquid components of the self-adhesive composition, such as
plasticizers, crosslinkers and/or further tackifier resins,
optionally in the melted state, to the compounding section, d)
preparing a homogeneous self-adhesive composition in the
compounding section, and e) discharging the self-adhesive
composition.
It has been found particularly advantageous to use, as the
continuously operating apparatus, a planetary roll extruder whose
compounding section consists preferably of at least two, but with
particular preference three, coupled roll cylinders, it being
possible for each roll cylinder to have one or more separate
temperature control circuits.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 illustrates one of the planetary roll extruder
configurations used in the Examples
FIG. 2 illustrates the route of the self-adhesive composition from
the upstream apparatus to the point of coating on to a carrier
material.
FIG. 3 illustrates an advantageous embodiment of the entire process
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Unlike otherwise conventional production processes, in the
planetary roll extruder in accordance with the process of the
present invention, in particular, there is no property-impairing
mastication of the non-thermoplastic elastomers, since in this case
they are not subjected separately to the effect of high shear
energy but instead are always processed together with one or more
liquid components. These liquid components can include both
plasticizers such as oils, for example, and also resins which only
melt during the compounding process under the action of shear
energy and/or external heating. The presence of these liquid
components limits the extent of frictional energy such that it is
possible to avoid the mastication of the rubber, i.e. the molecular
weight breakdown of the elastomers, and high resultant compounding
temperatures.
Furthermore, planetary roll extruders have extremely large areas
where material exchange and surface renewal take place, by which
means it is possible to dissipate rapidly the frictional shear
energy and thus to avoid undesirably high product temperatures.
The filling section of the roll cylinder consists of a conveying
screw to which all of the solid components are fed continuously.
The conveying screw then passes the material to the compounding
section. The area of the filling section, together with the screw,
is preferably cooled in order to prevent baking-on of materials on
the screw. Alternatively, there are designs without a screw
section, where the material is fed directly between central
spindles and planetary spindles. However, this is not important for
the effectiveness of the process of the invention.
As already stated, the number of planetary spindles has an effect
on the compounding result by way of the shear energy introduced:
given a constant roll cylinder diameter, a larger number of
spindles can be used to achieve better homogenization and
dispersion or a greater product throughput. In accordance with the
present invention, preferably at least half, with particular
preference at least 3/4, of the possible number of planetary
spindles are to be used in order to obtain a good ratio of
compounding quality to product rate.
For the process of the invention it is advantageous to use a
planetary roll extruder whose compounding section has been extended
by coupling at least two roll cylinders. Firstly, despite the
presence of friction-reducing components for the purpose of
avoiding mastication of the rubber, the complete digestion of the
elastomer components, and the desired homogenization and dispersion
at economic throughput rates, is possible by this means; secondly,
the coupling of, preferably, separately temperature-controlled roll
cylinders permits a balanced temperature regime of the process, so
allowing the use of heat-activatable crosslinker systems.
Whereas in the front compounding section of the planetary roll
extruder the roll cylinders are advantageously heated at
temperatures above the melting point of the resins used, the rear
compounding section is advantageously cooled in order to reduce the
product temperature. By this means, the residence time of the
self-adhesive composition at relatively high temperatures is kept
as low as possible, thereby preventing the activation of the
thermal crosslinker systems present in the self-adhesive
composition.
Of course, any roll cylinder can be equipped differently in terms
of the number and nature of the planetary spindles and so can be
adapted to the particular formulation and processing requirements.
Between two coupled roll cylinders there is generally an approach
ring through whose free cross section the central spindle is guided
and which holds the planetary spindles of a roll cylinder in fixed
location. Approach rings can have various free cross sections,
thereby allowing the holdup of the product, and thus the filling
level and/or extent of shear energy, to be varied and to be adapted
to the requirements of the process. In addition, the approach rings
can be provided with radial bores through which fluids such as, for
example, plasticizer oils or else inert gases such as nitrogen,
argon, carbon dioxide or the like can be supplied to the
compounding section of the planetary roll extruder.
The central spindle, and each roll cylinder as well, should
preferably have one or more separate temperature control or cooling
circuits in order to allow a temperature regime which permits the
use of heat-activatable crosslinking systems. In cases where this
is unnecessary, the temperature control circuits of coupled roll
cylinders can also be combined with one another in order to
minimize the number of temperature control devices.
For the purposes of the invention, the filling section of the
planetary roll extruder, and the central spindle, should be
preferably not heated but instead cooled, in order to prevent
baking-on of material on the filling screw and to ensure effective
heat exchange with the adhesive composition.
In the process according to the present invention, all solid
components, such as elastomers, fillers and adjuvants, resins,
ageing inhibitors, etc., are metered together into the filling area
of the planetary roll extruder. These substances can be added
either as separate components in each case or else as a conjoint
premix or else as partial premixes to the compounding apparatus.
Metering in the components in the form of a premix is particularly
appropriate if the components are in similar supply forms or have
similar bulk densities, so that in this way the number of metering
systems can be minimized. Premixes can be produced in a simple
manner, for example, in powder mixers. Metering of the individual
solid components takes place suitably by means of volumetric and
gravimetric metering systems in customary designs. A further
possibility is to add the fluid components, or only some of them,
such as plasticizer oil, for example, to a premix.
The materials metered in are transported by the screw of the
filling section into the first roll cylinder of the planetary roll
extruder. Between each roll cylinder, fluid components such as, for
example, plasticizer oils, soft resins or resin melts can be added
via bores in the approach rings. The amount of liquid added prior
to the influence of shear energy can be used to influence both the
degree of breakdown of the elastomers and the compounding
temperature of the pressure-sensitive adhesive composition. For
example, a particularly low level of molecular weight breakdown of
the elastomers is obtained if a liquid plasticizer is added at a
point in time when there has still been no influence whatsoever of
frictional energy, i.e. when this plasticizer is either added to a
solids premix or the plasticizer oil is metered in continuously
between the filling screw and the first roll cylinder. Also
possible is the subdivision of the liquid components, in the form
of a so-called split feed, over the barrel length, and this is
another parameter for controlling the process in terms of elastomer
breakdown and product temperature.
The process of the invention permits the production of
high-performance self-adhesive compositions and, especially in
conjunction with a downstream coating and crosslinking unit,
permits the production of high-performance self-adhesive tapes
accompanied by particular cost advantages.
The process consists essentially of the above process steps, which
can be carried out optionally under an inert gas atmosphere in
order to avoid oxidative polymer degradation.
In the first process step, a composition comprising the elastomers
and the known adjuvants required for the production of
self-adhesive compositions, such as fillers, ageing inhibitors,
plasticizers and tackifier resins, is produced solvent-free in a
planetary roll extruder, the composition having a final temperature
of less than 150.degree. C., preferably less than 130.degree. C.
and, with very particular preference, between 70.degree. C. and
110.degree. C. The overal residence time of the composition in the
planetary roll extruder should not exceed three minutes. The
resulting hot-melt adhesive composition has a viscosity of between
300 and 1500 Pa*s, in particular a viscosity of between 800 and
1200 Pa*s at 130.degree. C. under a shear rate of 100 rad/s.
In the second process step, which takes place advantageously in
conjunction with the compounding step in the planetary roll
extruder, the pressure-sensitive hot-melt adhesive composition
which is produced in accordance with the invention is coated
solvent-free onto a carrier in web form, using an applicator
unit.
Depending on the viscosity of the self-adhesive composition,
various processes are suitable for coating the web-form materials.
Self-adhesive compositions having viscosities of up to 5000 Pa*s
under a shear rate of 1 rad/s, as are obtained, for example, using
relatively high proportions of plasticizer oils or by adding
thermoplastic elastomers to the non-thermoplastic elastomers, can
be coated by means of an extrusion die downstream of the planetary
roll extruder, the preferred extrusion die used being a coathanger
manifold die. In order to obtain a defined, full-area application
of composition on the web-form material, it is advantageous for the
self-adhesive composition to be subjected to devolatilization
before entering the coating die, this being particularly important
in the case where inert gases are used during the compounding
process in the planetary roll extruder.
In accordance with the process of the present invention, the
devolatilization takes place under the action of reduced pressure,
preferably in screw machines which are at the same time able to
overcome the pressure drops of the pipelines and coating die. For
this purpose, particular preference is given to single-screw
extruders which in addition have a pressure regulation system, so
that the coating of the web-form carrier materials can take place
with amounts of applied composition with a very low range of
fluctuation.
A further possibility for the coating of the web-form carrier
materials with the self-adhesive composition produced by processes
in accordance with the invention is to use roller coating
applicator units or multi-roll coating calenders consisting of
preferably three, with particular preference four, coating rolls,
the self-adhesive composition being shaped to the desired thickness
as it passes through one or more roll nips before transfer to the
web-form material. This coating process is particularly preferable
when the viscosities of the self-adhesive composition exceed levels
of 5000 Pa*s under a shear rate of 1 rad/s, since in this case
coating with extrusion dies no longer provides the necessary
accuracy in terms of the amount of composition applied.
Depending on the nature of the web-form carrier material to be
coated, coating can be carried out by the co-rotating or
counter-rotating process.
Coating on roller coating applicator units or multi-roll coating
calenders is possible at temperatures below 100.degree. C., so that
even self-adhesive compositions containing heat-activatable
crosslinkers can be coated. For the purpose of increased freedom
from gas bubbles in the coated adhesive composition, it is possible
to install a vacuum devolatizer between the planetary roll extruder
and the applicator unit; for example, a vacuum chamber, a
devolatilizing extruder or the like.
Advantageously in conjunction with production of the composition
and coating, in a third process step, the self-adhesive composition
on the carrier is crosslinked by means of ionizing radiation, such
as electron beams, for example, so that the resultant self-adhesive
tape becomes shear-resistant and temperature-stable. UV rays as
well can be used for crosslinking, in which case appropriate UV
promoters must be added to the self-adhesive composition.
For further improved performance, or in the case of EBC-sensitive
carriers, crosslinking can also be carried out by means of
heat-activatable crosslinkers under the effect of temperature.
The heating of the pressure-sensitive hot-melt adhesive composition
that is required for this purpose can be done with the aid of the
known techniques, especially with the aid of high-temperature
ducts, or else with the aid of infrared lamps, or by means of
high-frequency magnetic alternating fields, examples being HF
waves, UHF waves or microwaves.
Crosslinking of the pressure-sensitive hot-melt adhesive
composition can be carried out, furthermore, by means of a
combination of ionizing radiation and heat-activatable chemical
crosslinkers.
The result is a highly shear-resistant pressure-sensitive
self-adhesive composition whose properties are comparable with
those of similar self-adhesive compositions produced in a solvent
process.
With the process of the invention, virtually without exception, all
known components, described in the literature, of rubber-based
self-adhesive compositions can be processed without solvent.
Advantageously, the non-thermoplastic elastomer is chosen from the
group of the natural rubbers or of the synthetic rubbers or
consists of any desired blend of natural rubbers and/or synthetic
rubbers, it being possible to choose the natural rubber or rubbers
in principle from all available grades, such as, for example,
crepe, RSS, ADS, TSR or CV grades, depending on the required purity
and viscosity level, and it being possible to choose the synthetic
rubber or rubbers from the group of the randomly copolymerized
styrene-butadiene rubbers (SBR), butadiene rubbers (BR), synthetic
polyisoprenes (IR), butyl rubbers (IIR), halogenated butyl rubbers
(XIIR), acrylate rubbers (ACM), ethylene vinyl acetate copolymers
(EVA) and polyurethanes, and/or blends thereof.
With further preference, thermoplastic elastomers with a weight
fraction of from 10 to 50% by weight, based on the overall
elastomer content, can be added to the non-thermoplastic elastomers
in order to improve their processability.
As representatives, mention may be made at this point in particular
of the highly compatible styrene-isoprene-styrene (SIS) and
styrene-butadiene-styrene (SBS) grades.
Tackifier resins which can be used are, without exception, all
tackifier resins known to date and described in the literature.
Representatives that may be mentioned include the rosins, their
disproportionated, hydrogenated, polymerized and esterified
derivatives and salts, the aliphatic and aromatic hydrocarbon
resins, terpene resins and terpene-phenolic resins. Any desired
combinations of these and other resins can be used in order to
adjust the properties of the resultant adhesive composition in
accordance with what is desired. Reference may be made expressly to
the depiction of the state of knowledge in "Handbook of Pressure
Sensitive Adhesive Technology" by Donatas Satas (van Nostrand,
1989).
Plasticizers which can be used are all plasticizing substances
known from adhesive tape technology. They include, inter alia, the
paraffinic and naphthenic oils, (functionalized) oligomers such as
oligobutadienes and oligoisoprenes, liquid nitrile rubbers, liquid
terpene resins, animal and vegetable oils and fats, phthalates, and
functionalized acrylates.
For the purpose of heat-induced chemical crosslinking, it is
possible in the process of the invention to use all known
heat-activatable chemical crosslinkers, such as accelerated sulphur
or sulphur donor systems, isocyanate systems, reactive melamine
resins, formaldehyde resins and (optionally halogenated)
phenol-formaldehyde resins and/or reactive phenolic resins or
diisocyanate crosslinking systems with the corresponding
activators, epoxidized polyester resins and acrylate resins, and
combinations thereof.
The crosslinkers are preferably activated at temperatures above
50.degree. C., in particular at temperatures from 100.degree. C. to
160.degree. C. and, with very particular preference, at
temperatures from 110.degree. C. to 140.degree. C.
The thermal excitation of the crosslinkers can also be effected by
means of IR rays or high-energy alternating fields.
Further embraced by the concept of the invention is a self-adhesive
tape produced with the aid of the pressure-sensitive hot-melt
adhesive composition by applying the self-adhesive composition to
at least one side of a material in web form.
Depending on the intended use of the adhesive tape, suitable
web-form carrier materials for the self-adhesive compositions
processed and produced in accordance with the invention are all
known carriers, with or without appropriate chemical or physical
surface pretreatment of the coating side, and anti-adhesive
physical treatment or coating of the reverse side. Mention may be
made, for example, of creped and non-creped papers, polyethylene,
polypropylene and mono- or biaxially oriented polypropylene films,
polyester, PVC and other films, foam materials in web form, made
from polyethylene and polyurethane, for example, wovens, knits and
nonwovens.
Finally, the web-form material can be a material with an
antiadhesive coating on both sides, such as release papers or
release films. The thickness of the self-adhesive composition on
the web-form material can be between 10 .mu.m and 2000 .mu.m,
preferably between 15 .mu.m and 150 .mu.m.
Finally, the self-adhesive composition can be applied in a
thickness of from 800 .mu.m to 1200 .mu.m on a release paper. An
adhesive-composition layer of this kind, especially after
crosslinking, can be used diversely as a backingless double-sided
self-adhesive tape.
Owing to the high molecular weight of the unmasticated elastomers,
the process of the invention provides for the first time the
possibility of being able either to do away entirely with
crosslinking the pressure-sensitive adhesive composition or else to
carry out effective crosslinking which permits, for example,
high-temperature applications of the adhesive tapes produced by
this process, by means of high-energy radiation, without the need
for promoters for this purpose. Furthermore, as a result of the
temperature regime at a lower level, it is now also possible for
the first time to use heat-activatable crosslinkers in the
production of solvent-free self-adhesive compositions on the basis
of non-thermoplastic elastomers, such as rubbers having a molecular
weight M.sub.w.gtoreq.1 million.
The self-adhesive compositions produced in accordance with the
process of the invention are highly shear-resistant. The rubbers
used are not subjected to mastication, but in the individual
process steps degradation processes occur which do not, however,
durably impair the properties of the self-adhesive composition.
Furthermore, these processes are restricted and are manageable as a
result of the process of the invention.
The invention is described in more detail below with reference to
the following examples, without wishing thereby to restrict the
invention.
The test methods used are briefly characterized as follows:
The bond strength (peel strength) of the compositions was
determined in accordance with AFERA 4001.
The shear strength of the adhesive compositions investigated was
determined in accordance with PSTC 7 (holding power). All values
given were determined at room temperature under the stated loads of
10 or 20 N, with a bond area of 20.times.13 mm.sup.2. The results
are reported in minutes of holding time.
In the examples, a planetary roll extruder from the company ENTEX
Rust & Mitschke was used. The diameter of a roll cylinder was
70 mm, its length being varied between 400 mm and 1200 mm. FIG. 1
shows one of the planetary roll extruder configurations used in the
examples below.
The planetary roll extruder has a filling section (2) and a
compounding section (5) consisting of three roll cylinders (5a-5c)
in series. Within one roll cylinder, the planetary spindles (7)
driven by the rotation of the central spindle (6) exchange the
materials between central spindle (6) and planetary spindles (7)
and between planetary spindles (7) and the wall of the roll
cylinder (5a-5c). The rotary speed of the central spindle (6) was
steplessly adjustable to up to 110 revolutions per minute.
At the end of each roll cylinder (5a-5c) there is an approach ring
(8) which holds the planetary spindles (7) in fixed location.
By way of the filling port (1), all solid components of the
solvent-free self-adhesive composition, such as elastomers, resins,
fillers, antioxidants, etc., were metered on to the conveying screw
(3) of the filling section (2) of the planetary roll extruder. The
conveying screw (3) transfers the materials, subsequently, to the
central spindle (6) of the first roll cylinder (5a). In order to
improve the intake of material between central spindle (6) and
planetary spindles (7), six planetary spindles (7) of different
lengths in alternation were used in the first roll cylinder
(5a).
The internally hollow conveying screw (3) and central spindle (6)
are non-positively connected to one another and possess a common
temperature control circuit. Each roll cylinder (5a-5c) of the
compounding section (5) possessed two separate temperature control
circuits. The filling section (2) was cooled by way of a further
temperature control circuit. The temperature control medium used
was pressurized water, cooling taking place with cooling water at
from 15.degree. C. to 18.degree. C.
The separate metered addition of liquids such as plasticizer oil
and/or crosslinker was made by way of the injection ring (4) in
front of the first roll cylinder (5a) and/or by way of the approach
rings (8a, 8b), which are provided with bores, or by a combination
of both possibilities.
The temperature of the self-adhesive composition was determined by
means of probes at the product discharge point (9).
The intention below is to illustrate the process of the invention
by means of further figures without wishing thereby to restrict the
invention unnecessarily.
Shown in
FIG. 2 is the route taken by the self-adhesive composition from the
upstream apparatus, preferably a planetary roll extruder, to the
point of coating on to a carrier material, and in
FIG. 3 is an overview of the entire process in a particularly
advantageous embodiment.
In accordance with FIG. 2, the strand (11) of the self-adhesive
composition comes from the upstream apparatus, preferably a
planetary roll extruder, into a conveying extruder (12). In this
extruder (12) the self-adhesive composition is freed from air via
an aperture (16) with the aid of vacuum and is conveyed into a
coating nozzle having a coathanger manifold (13), with which the
self-adhesive composition is applied to the carrier material (15),
which runs over a cooling roll (14).
FIG. 3, finally, gives an overview of the entire process in a
particularly advantageous embodiment. In the first process step,
the self-adhesive composition (28) is compounded in a planetary
roll extruder (21). The finished self-adhesive composition (28) is
conveyed into a melt pump (22) which transfers the self-adhesive
composition (28) into a roll applicator unit.
After compounding under an inert gas atmosphere, there is a
devolatilizing extruder (23) between melt pump (22) and roll
applicator unit for the purpose of obtaining an air-bubble-free
self-adhesive composition (28). The roll applicator unit is formed
by a metering roll (24), a coating-bar roll (25), which determines
the thickness of the self-adhesive layer (28) on the carrier
material (29), and a transfer roll (26). On a layup roll (27),
finally, the self-adhesive composition (28) and the carrier
material (29) are brought together and so form a laminate (30).
EXAMPLES
Comparative Examples 1 to 3
The efficiency of a planetary roll extruder in terms of the
achieveable throughput when using a plurality of roll cylinders in
series for the process of the invention for the solvent-free
production of self-adhesive compositions based on non-thermoplastic
elastomers is shown by Comparative Examples 1 to 3. The planetary
roll extruder used was as described in principle in FIG. 1. With
the same formulation and under otherwise constant conditions, the
planetary roll extruder was operated in each case with one, two or
three roll cylinders, each roll cylinder being equipped with 6
planetary spindles and an approach ring having a free cross section
of 44 mm being used between each roll cylinder. The rotary speed of
the central spindle was set at 100 revolutions/minute. For each
planetary roll extruder configuration, the maximum product rate
(Q.sub.max) up to which a homogeneous compound was obtained was
determined.
In Examples 1 to 3, formulation A was used. In these and all
subsequent examples, the non-thermoplastic elastomers were used in
the form of granules having average particle sizes of 8 mm. In
order to keep the granules meterable, they were treated with talc.
The granules were produced using a cutting mill from Pallmann.
Exemplary formulation A Weight fraction A Component [phr] NR Air
Dried Sheets 100 Zinc oxide, active 11.4 Escorez 1202 .RTM. 43.6
Dercolyte S115 .RTM. 20 Resin 731 D .RTM. 50.9 Ondina G 33 .RTM. 8
Lowinox AH 25 .RTM. 2.5 Total 236.4
All of the components of the formulation were used to produce, in a
50 kg powder mixer, a premix which was metered via a volumetric
metering system into the filling section of the planetary roll
extruder. The temperature control circuits for the central spindle
and the filling section (TK1 and TK2) were water-cooled, and each
roll section was heated at 100.degree. C. The table shows the
maximum product rates obtained as a function of the number of roll
cylinders.
Comparative Number of Q.sub.max Example roll cylinders [kg/h] 1 1
45 2 2 62 3 3 83
Example 4
For the production of masking tapes based on paper backings, the
formulation used was formulation A from Examples 1-3. The
composition was produced in a planetary roll extruder in analogy to
Example 3. The discharge temperature of the composition was
112.degree. C.
The adhesive composition obtained in this way, immediately after
the production process, was applied with a layer thickness of 40
.mu.m to a slightly creped paper backing having a basis weight of
68 g/m.sup.2 which had been impregnated by industry-standard
processes and provided with a known release layer and primer layer.
The adhesive composition was coated with the aid of a 4-roll
calender applicator unit from Farrel in an operating width of 1200
mm with supply of the composition through a single-screw conveying
extruder. Coating took place in synchronism, i.e. the adhesive was
transferred to the creped paper by the third calender roll, which
determined the amount of adhesive applied, with the aid of a
web-guiding contact roll (rubber).
The adhesive emerging from a conveying extruder was conveyed at
changed speed into the upper roll nip of the calender with the aid
of a conveyor belt. By virtue of the nip established between the
two upper rolls of the calender, a pre-metering of composition is
achieved which produces an adhesive film approximately 2 to 3 cm
thick. This preformed film of composition is taken off by the third
roll and shaped to the desired application of composition by means
of the nip established with respect to the third roll. The third
roll undertakes transfer to the substrate, which is guided via a
contact roll, at web speed in synchronism.
Between the rolls, a differential speed was established in a ratio
of 6:1. All rolls were temperature controlled to 113.degree. C. The
coating speed was 150 m/min.
The adhesive tape obtained in this way has a bond strength of 3.5
N/cm, shear hold times (10N) of >1000 minutes, and is suitable
as a masking tape with short-term thermal stability of up to
80.degree. C.
After coating, the adhesive composition applied to the adhesive
tape thus obtained was crosslinked by means of electron beams.
Irradiation was carried out on a scanning accelerator from POLYMER
PHYSIK, Tubingen, with an acceleration voltage of 175 kV and a
radiation dose of 20 kGy.
With unchanged bond strength, the shear hold times (10N) measured
in the same way increased to >5000 minutes and the resulting
tape was suitable as a masking tape with short-term temperature
stability of up to 120.degree. C.
Example 5
A high-temperature masking tape based on a paper backing was
produced using the following exemplary formulation B.
Exemplary formulation B Weight fraction B Component [phr] NR Air
Dried Sheets 100 Zinc oxide, active 11.4 Stearic acid 1.1 Escorez
1202 .RTM. 20 Dercolyte S115 .RTM. 43.6 Resin 731 D .RTM. 50.9
Ondina G 33 .RTM. 8 Lowinox AH 25 .RTM. 2.5 Rhenogran S 80 .RTM.
3.1 Rhenogran ZEPC 80 .RTM. 4.4 Rhenocure HX .RTM. 0.5 Total
245.5
The composition was produced in a planetary roll extruder as in
FIG. 1 having three roll cylinders. The first roll cylinder was
equipped with six planetary spindles, the second and third roll
cylinders each with seven. The rotary speed chosen for the central
spindle was 110 rpm.
The temperature control circuits 1 to 3 and 7 to 8 were operated
with cooling water at 18.degree. C.; temperature control circuits 4
to 6 were heated at 95.degree. C. The discharge temperature of the
composition was found to be 99.degree. C.
All of the components were premixed and this premix was metered
continuously at a rate of 66 kg/h into the filling section of the
planetary roll extruder.
Immediately after the production process, the adhesive composition
obtained in this way was applied with a layer thickness of 55 .mu.m
to a moderately creped paper backing having a basis weight of 85
g/m.sup.2 which had been impregnated by industry-standard processes
and provided with known release and primer layers.
The adhesive composition was coated as in Example 4 in a working
width of 500 mm. All rolls were temperature controlled to
113.degree. C. The coating speed was 60 m/min.
After coating, the adhesive composition applied to the adhesive
tape obtained in this way was crosslinked by means of electron
beams as in Example 4. The radiation dose was 25 kGy.
The adhesive tape obtained in this way had a bond strength of 4.5-5
N/cm, shear hold times (10N) of more than 10,000 minutes, and was
suitable as masking tape having short-term temperature stability of
up to 140.degree. C.
Example 6
The adhesive of the adhesive tape produced in accordance with
Example 5 was crosslinked not with electron beams but instead
chemically under the action of temperature.
Crosslinking took place in a vulcanization tunnel with an effective
residence time of 4 min/120.degree. C.
The temperature stability of the tape obtained in this way
increased to 160.degree. C.
Example 7
Packaging tape prototypes based on film were produced using the
following exemplary formulation C.
Exemplary formulation C Weight fraction C Component [phr] SMR L 100
Dercolyte S 115 .RTM. 104 ASM Lowinox AH 25 .RTM. 2 Total 206
The abovementioned components were supplied continuously but
separately via volumetric metering systems to the filling section
of the planetary roll extruder. The process parameters were
otherwise as in Example 4. The product discharge temperature was
measured as 122.degree. C.
Immediately after the production process, the adhesive composition
obtained in this way was applied with a layer thickness of 20 .mu.m
to an industry-standard 30 .mu.m BOPP film provided with an
industry-standard primer layer based on isocyanate and with an
industry-standard release layer based on carbamate.
The adhesive composition emerging from a conveying extruder was
coated with the aid of a flexurally rigid 2-roll applicator unit.
The adhesive film was coated directly onto the primed film side. A
coating nib corresponding to the applied thickness was established
between the first and the second, web-guiding coating roll. The
first roll was temperature contolled to 100.degree. C., the
web-guiding roll to 90.degree. C. The adhesive composition emerging
from the conveying extruder had a temperature of 120.degree. C.
Coating was carried out at 50 m/min.
The adhesive tapes obtained in this way had a bond strength of 3-4
N/cm and shear hold times (20N) of >10,000 minutes, and are
suitable as adhesive tapes for packaging purposes.
Example 8
Double-sided adhesive tapes based on film backings were produced
using the following exemplary formulation D.
Exemplary formulation D Weight fraction D Component [phr] Rubber
ADS 100 Dercolyte S 115 .RTM. 104 Sunpar Oil 2280 .RTM. 2 ASM
Lowinox AH 25 .RTM. 2 Total 208
The composition was produced as in Example 7. In addition, the
liquid plasticizer was metered continuously via the injection ring
upstream of the first roll cylinder with the aid of a membrane
piston pump. The product discharge temperature was measured as
105.degree. C. The product rate was 68 kg/h.
Immediately after the production process, the adhesive composition
obtained in this way was applied with a layer thickness of
2.times.40 .mu.m to both sides of a commercial 38 .mu.m E-PVC
film.
Coating took place with the aid of the applicator unit from Example
5. The adhesive composition was applied to the E-PVC film
indirectly in reverse mode. Coating was carried out at a speed of
50 m/min. The transfer roll was operated at 85% of the web speed.
Roll 1 and roll 2 were temperature controlled at 100.degree. C. and
80.degree. C. respectively. The web-guiding roll was temperature
controlled to 30.degree. C. Directly after coating, the adhesive
side was lined with a double-sided silicone paper. The assembly was
then coated by the same process as the first side, and rolled
up.
The adhesive tapes obtained in this way have a bond strength of 7.5
N/cm and shear hold times (10N) of >5000 minutes; they are
suitable as double-sided adhesive tapes for a wide variety of uses,
such as for the adhesive bonding of plates in the printing
industry.
Example 9
A double-sided carpet-laying tape based on woven backing was
produced using the following exemplary formulation E.
Exemplary formulation E Weight fraction E Component [phr] SMR L 100
Escorez 1202 .RTM. 55 Dercolyte S 135 .RTM. 55 Wingtack 10 .RTM. 15
Zinc oxide Harzsiegel .RTM. 22 ASM Lowinox AH 25 .RTM. 2 Total
247
The composition was produced using a planetary roll extruder
configuration as mentioned in Example 5 with a central spindle
rotary speed of 95 rpm. For the purpose of metering liquids, the
approach rings after the first and second roll cylinder were
provided with radial bores. The free cross sections in the approach
rings in this example were 46 and 44 mm respectively.
Via the temperature control circuits 4 to 6, the roll cylinders
were heated at 105.degree. C.; temperature control circuits 1 to 3
and 7 to 8 were cooled with water at a temperature of 15.degree.
C.
Except for the Escorez and Dercolyte resins, the components of the
formulation were metered via separate volumetric metering systems.
The two resins were formed beforehand in a powder mixer into a
premix which was then metered in. The viscous soft resin Wingtack
10 was preheated to 60.degree. C. for easier meterability and was
metered in in the injection ring upstream of the first roll
cylinder by way of a pipeline accompanied by electrical heating.
The metering pump used was a double-action piston metering pump
whose reservoir container had a heated and heat-insulated jacket
which was temperature controlled to 60.degree. C. The product
discharge temperature was measured as 109.degree. C. The product
rate was 65 kg/h.
Immediately after the production process, the adhesive composition
obtained in this way was applied with a layer thickness of
2.times.120 .mu.m to both sides of a commercial woven spun rayon
(yarn density 19/17).
A double-sided carpet-laying tape based on woven backing was
produced with the aid of transfer coating. A release paper
siliconized on both sides was coated directly with 120 .mu.m by the
process from Example 4. By way of a laminating station, the
commercial raw spun rayon fabric was laminated on and in a second
operation the assembly was coated likewise directly with 120 .mu.m
of adhesive on the exposed side. The temperature of the adhesive
composition was 103.degree. C. The coating rolls were temperature
controlled to 90.degree. C. The raw spun rayon fabric was supplied
by way of a heated laminating station, the first laminating roll
having a siliconized surface coating and the second, web-guiding
laminating roll being temperature controlled to 80.degree. C.
Coating took place at a speed of 30 m/min.
The adhesive tapes obtained in this way have a bond strength of
>7 N/cm and shear hold times (10N) of more than 200 minutes;
they are suitable as double-sided adhesive tapes for a wide variety
of purposes, especially for carpet-laying work.
Example 10
General-purpose adhesive tapes with different woven backings were
produced using the following exemplary formulation F.
Exemplary formulation F Weight fraction F Component [phr] SMR L 70
Cariflex IR 305 .RTM. 30 Escorez 1202 .RTM. 55 Picco 5120 .RTM. 55
Wingtack 10 .RTM. 50 Sunpar Oil 2280 .RTM. 15 ZnO Harzsiegel .RTM.
50 ASM Butyl Zimate .RTM. 2 Total 325
This self-adhesive composition was produced using the same
experimental setup as in Example 9.
Premixes were prepared respectively from the two solid resins, from
the two pulverulent components and from the two elastomers, and
these premixes were added to the filling section of the planetary
roll extruder, separately, by way of volumetric metering devices.
The plasticizer oil was added with the aid of a membrane piston
pump via the injection ring upstream of the first roll cylinder;
the soft resin, preheated to 60.degree. C., was added via the
approach ring downstream of the first roll cylinder by means of a
double-action piston metering pump. All components were metered so
as to give a product rate of 62 kg/h. The product discharge
temperature was measured at 105.degree. C.
The adhesive composition obtained in this way was applied with a
layer thickness of 120 .mu.m to a polyester/cotton blend fabric
with a yarn density of 22/10, with an 80 .mu.m polyethylene layer
laminated on, which is provided on its reverse side with an
industry-standard carbamate release varnish.
General-purpose woven-backed tapes were produced by the process of
Example 4. In this case, instead of the paper backing web, the
polyester/cotton blend fabric and the polyethylene film were guided
over the contact roll and the 120 .mu.m thick adhesive layer,
shaped by the roll coating calender, was coated onto the
polyester/cotton blend fabric. Coating took place at 155 m/min in a
working width of 1200 mm. The coating rolls were operated in a
ratio of 6:1. The tape produced in this way has a bond strength of
>5 N/cm and is suitable as a general-purpose adhesive tape for a
very wide variety of purposes.
Example 11
An adhesive composition was produced in accordance with exemplary
formulation G.
Exemplary formulation G Weight fraction G Component [phr] SMR L 100
Stearic acid 1.1 Escorez 1202 .RTM. 55 Dercolyte S 135 .RTM. 55
Wingtack 10 .RTM. 15 Zinkoxyd aktiv .RTM. 22 ASM Lowinox AH 25
.RTM. 2 Rhenogran S 80 .RTM. 4.4 Rhenogran ZEPC 80 .RTM. 4.4
Rhenocure HX .RTM. 0.6 Total 259.5
The adhesive composition was produced in a planetary roll extruder
in accordance with FIG. 1 having three roll cylinders and equipped
with planetary spindles as in Example 5. The rotary speed of the
central spindle was set at 100 rpm.
To produce the self-adhesive composition containing thermal
crosslinkers, the temperature control circuits 1 to 3 and 7 to 8
were operated with cooling water at 16.degree. C. while the
temperature control circuits 4 to 5 were heated at 110.degree. C.
and the temperature control circuit 6 at 95.degree. C. With this
temperature regime, a composition discharge temperature of
98.degree. C was obtained.
All of the solid components were combined to form a meterable
premix which was metered continuously into the filling section of
the planetary roll extruder. The liquid resin Wingtack 10 was added
in preheated form as in Example 9 by means of a piston metering
pump. In order to keep the residence time of the thermal
crosslinker Rhenocure HX at elevated temperatures as short as
possible, it was metered in via the second approach ring, i.e.
upstream of the third roll cylinder, continuously by means of a
peristaltic pump. In this example, operation took place with a
product rate of 75 kg/h.
Directly after the production process, the adhesive composition
obtained in this way was applied with a layer thickness of 1000
.mu.m to a customary release paper with release coating on both
sides.
The release paper siliconized on both sides was coated directly
with 1000 .mu.m by the process from Example 7. Coating took place
at a speed of 30 m/min.
Subsequently, crosslinking was carried out in a vulcanizing tunnel
with an effective residence time of 4 min/80.degree. C.
The coated release paper obtained in this way constitutes a
double-sided adhesive tape which can be put to diverse uses. It can
be utilized, for example, as an assembly aid, for the self-adhesive
treatment of parts to be joined or profiles, and for the transfer
of the adhesive film to other carriers.
Example 12
A double-sided carpet-laying tape based on woven backing was
produced with the exemplary formulation H.
Exemplary formulation H Weight fraction H Component [phr] Rubber
ADS 100.0 Hercurez C 54.9 Escorez 1202 41.4 Plasticizer Nipol 17.5
Zinkoxyd aktiv 7.5 Silitin Z 86 24.7 Stearic acid 1.0 ASM Lowinox
AH 25 2.5 Total 249.5
The self-adhesive composition was produced in a planetary roll
extruder as per FIG. 1 having three roll cylinders and equipped
with planetary spindles as mentioned in Example 5. The planetary
roll extruder was operated with a central spindle rotary speed of
110 rpm.
The temperature control circuits 1 to 3 and also temperature
control circuit 8 were operated with cooling water at 16.degree. C.
The temperature control circuits 4 to 5 were heated at 120.degree.
C. and the temperature control circuits 6 to 7 at 100.degree. C.
This gave a temperature of the composition at the outlet from the
planetary roll extruder of 112.degree. C.
In analogy to Example 11, all solid components were combined to
form a meterable premix which was metered into the filling port of
the planetary roll extruder. The viscous plasticizer Nipol was
preheated to 75.degree. C. for easier meterability and was added
via the approach ring upstream of the second roll cylinder with the
aid of the double-action piston metering pump from Example 9. The
product rate established was 81 kg/h.
With the aid of transfer coating, the adhesive composition was
applied with a layer thickness of 2.times.55 g/m.sup.2 to both
sides of a commercial polyethylene-based foam material having a
thickness of 1000 .mu.m and a density of 95 kg/m.sup.3.
A double-sided carpet-laying tape based on woven backing was
produced. A release paper siliconized on both sides was coated
directly with 55 .mu.m by the process from Example 8. In a
laminating station, the PE foam is laminated on and in a second
operation the assembly is coated likewise directly with 55 .mu.m of
adhesive onto the exposed side. The temperature of the adhesive
composition was 100.degree. C. The coating rolls were temperature
controlled to 90.degree. C. The PE foam material was supplied by
way of a heated laminating station, the first laminating roller
having a siliconized surface coating and the second, web-guiding
laminating roll being temperature controlled to 80.degree. C.
Coating took place at a speed of 30 m/min.
The adhesive tapes obtained in this way have a bond strength of
>3.5 N/cm and shear hold times (10N) of >250 minutes; they
are suitable as double-sided adhesive tapes having
tolerance-compensating and damping properties for a wide variety of
purposes.
* * * * *